NASHVILLE, Tenn. — Last week, when a Tennessee judge forcibly changed an infant's name from Messiah to Martin, it was hard to decide which was more noteworthy, the parents' grandiosity in naming their child for the one they consider their Savior or the judge's religious zealotry in prohibiting the name.

“The word 'Messiah' is a title, and it's a title that has only been earned by one person and that one person is Jesus Christ,” said Magistrate Lu Ann Ballew.

The American Civil Liberties Union has offered to appeal the ruling for the child's mother, Jaleesa Martin, of Newport, Tenn., who did not return a phone call.

The ruling came in a hearing after Ms. Martin and the baby's father could not agree on a last name for the boy, but the judge took issue with his first name.

The case of little Messiah — or Martin, for now — raises two interesting questions, one legal and the other religious. Both are trickier than they seem.

States put all sorts of restrictions on parental naming rights, from the length of first names to what punctuation marks are permissible.

But the restrictions cannot, for the most part, be justified by an appeal to religion. It therefore seems likely that Magistrate Ballew's ruling against “Messiah” will be overturned as a violation of the First Amendment.

On the other hand, last year a New York judge refused to allow a couple to change their family name to ChristIsKing.

The judge argued that allowing certain names could infringe on the religious liberties of others, and he offered the example of a court employee forced to call out a name with a religious message.

He was alluding to the daughter's first name, Rejoice, and a name they had sought for their son, although no court would allow them to change it to “JesusIsLord.”

Judge Straniere's decision is not binding in Tennessee, but it reminds us that whenever religious language is involved, whether etched into public buildings or slapped onto a Social Security card, there are competing claims of religious freedom.

The Tennessee magistrate might have argued that “Messiah” would infringe on the religious liberty of those who did not want to call this boy the messiah — or did not believe there was even such thing as a messiah. She could have been the defender of atheists' rights! That argument might have stood a better chance on appeal.

Last year, there were 762 American baby boys given the name Messiah, putting it right between old standbys Scott and Jay for popularity, according to the Social Security Administration database.

As currently formulated, the magistrate's reasoning would be a problem not only for all of them, but also for all the Americans, primarily of Hispanic ancestry, who have named their sons Jesus.

There were 3,758 Americans given the name Jesus last year, putting it way ahead of Messiah.

Now, one could argue that Jesus does not necessarily refer to Jesus Christ, the one believed to be the Messiah (“Christ” is one Greek-derived translation for “messiah”).

But surely that's whom most parents have in mind. Jesús finds particular favor among Roman Catholics in Mexico and Central America, where so many recent immigrants come from. It is less popular in Spain.

“My impression,” said Ilan Stavans, who teaches Spanish literature at Amherst College, “is that there is an identification in Latin America with characters of the Passion that you don't find in other parts of the world, including Spain.”

Yet as Mr. Stavans points out, the tradition of religious naming in Latin America goes beyond those involved in the events, known as the Passion, leading up to Jesus' crucifixion. Many Latinos are happy to name their children versions of the word “God.”

“Adonai is also a common name among Latinos, especially Mexicans,” Mr. Stavans said. “And so is Elohim.” Those are both Hebrew versions of the word for the deity.

“But neither of them,” he added, “matches the ubiquity of Jesus, closely followed by Maria, Jose and Guadalupe.”

Hebrew-derived names are particularly popular among Latinos who have become Pentecostal Protestants, according to Arlene Sánchez-Walsh, a historian at Azusa Pacific University, in Azusa, Calif.

As Pentecostalism has spread in Latin America, new adherents have a “desire to connect to Old Testament prophets, Jewish dietary laws and sometimes Sabbath keeping,” Ms. Sánchez-Walsh said. It “gives Latino Pentecostals a stake in their religious heritage as non-Catholics — which is what a lot of this is about.”

For some, that stake in non-Catholic Christianity is achieved by picking the names of patriarchs or prophetic figures, like Jacob or Eliezer, both names given to Hispanic Pentecostal boys I know. Adonai or Elohim ups the Old Testament ante.

Jews don't name children versions of God, generally sticking to human beings in the Hebrew Bible.

It is forbidden for Muslims to name a child Allah or God. For reasons that are unclear, much of the English-speaking world has tended to avoid Jesus as a name.

And all of these rules, quasi rules and traditions are subject to change, notes Stephen Butler Murray, the pastor of First Baptist Church in Boston and a lecturer at Harvard Divinity School.

“Mary was considered simply too holy for secular use until the 12th century,” Mr. Murray said. Yet today Mary, along with cognates like Maria and Marie, are popular throughout the Christian world.

Finally, Mr. Murray added that we use God-names for institutions all the time, without anyone being accused of blasphemy.

“Messiah College in Pennsylvania seems to go on without being struck by the lightning of divine wrath too often,” he said.